Method of applying inorganic insulation to electrical sheets



amed M... 13,1934 1,951,039

METHOD APPLYING INORGANIC INSULA- TION T ELECTRICAL SHEETS i Charles A. Scharschu, Brackenridge, Pa, assignor to Allegheny Steel Company, a corporation oi Pennsylvania No Drawing. Original application June 8,

1931, Serial No. 543,003. Divided and this application January 22, 1932, Serial No. 588,226

Claims. (Cl. 175-21) This invention relates toa method of applying I have found that very simple enamels are inorganic enamels to electrical sheets, this apsatisfactory for coating electrical sheets. For inplication being a division of my copending applistance water glass may be used as the source of cation Serial No. 543,003, filed June 8, 1931. By silicate although finely ground silica may also be 5 electrical sheets I mean steel sheets of su table used. To either of these there is added lime and composition and physical condition which are another metallic oxide such as iron oxide, the adapted for use in electrical apparatus. a proportions depending upon the properties de- Hitherto organic enamels or varnishes have sired in the enamel. been used to coat electrical sheets for the purpose Fo p t s three cflnstituents are used 0 of insulating one sheet from another in electrical in the following p opo for Qertain p apparatus, thus cutting down the eddy loss. tion I ere are, however, many applications for which this type of coating is objectionable, such as in Water 200 cc those cases where it is desired to anneal the i g fgg gg 3 3$: 15 punching after the enamel has been applies was. gas 1:333:33:3:333:33: gram.

For producing porcelainic enamels, silicates are generally used, but these enamels, on account of It is understood that magnesium oxide may be the properties desired, are more complex than is substituted for the lime, or both may be used, preferred in an enamel for electrical sheets and and that S ca, p e e a y in a finely ground 20 these enamels are, moreover, of such a composidition, may be substituted for the water glass,

tion and fired at such temperatures as to cause and the iron oxide may or may not be used dethe enamel to melt and flow. Enamels of this napending upon the properties desired in the ture consequently are not suitable for electrical enamel. sheets as such enamels would cause the indi- The sheets of material destined for electrical 25 vidual sheets to stick together when annealed in uses are passed singly through a bath of the liq- "stacks. Again, these enamels are much heavier. uid enamel, then through a set of rolls and and more continuous than is necessary for the through a drying oven to drive off the Wat insulation of electrical sheets. The rolls cause an even distribution of the liquid Inorganic enamels w p p y ade and enamel on the surfaces of the sheets andremove 30 applied have excellent electrical resistance and excess enamel and may he of any suitable type. may be used to coat electrical sheets. When in- If desired, or found necessary glue or an excess ganic enamels are used the electrical sheet may of water glass may be added'to the bath to make be enameled before it is P d cut to pa the enamel adhere more tightly to the sheet be-.

. for electrical apparatus and these punchings may for the sheets are heated.

35 be subsequently annealed to produce better elec- The drying oven i kept t a suitable t al qu al s with ut d s t y the am ture, for example, about 600 Fahrenheit, and the 0116 0 Objects t is invention s the P- coated sheets are assed therethrough at a suitplication of an inorganic insulation to electrical bl t such thgt the coating is subjected 1 0 sheets which will adhere to such electrical sheets th h t for about two minutes. The coat n is 40 and which can be uniformly deposited thereupon. finally baked on in th anneal which is carried Another object is to apply an inorganic insu1a out at about 1450 hrenheit, The tempera.- gg m fi g gg g f fg to an anneal wlthout ture of the drying oven may vary considerably A further object is application of an inor but in such cases the time of exposure thereto is suitably varied in inverse relationship thereto; 45 game enamel of certam composltmn which not that is the hotter the oven the less the time of only has the desired electrical properties but t th which acts as a protective coating for the sheets efmosure and the cooler the oven the grea er e to prevent rusting of the same time of exposure. In other words, the oven A till further object resides in the details, of treatment 15 under cmdltlons l 50 the present method of applying an inorganic inabout two mmutes at Pbout 600 sulating material so as to produce an even adher- I may Vary the consmuentsj Over wlde hmlts to ent coating having the desired characteristics. produce enamels havmg dlfferent properties, Other and further objects and advantages will Which, When baked at the p p p ll be d t d by th kill i thi t or will form an insulating enamel suitable for electrical 55 be apparent or pointed out hereinafter. sheets. This enamel, especially when applied to ,pickeled sheets, also acts as a protective coating preventing the sheets from rusting. What Iclaim as new and desire to secure-by Letters Patent is:

1. The method of applying an inorganic insulating material to steel sheets for use in electrical apparatus including the steps of passing the sheets through a bath ofthe liquid insulating material, then through. a set of distributing and wiping rolls and then through a drying oven under conditions corresponding to about two minutes at about 600 F.

2.,The method of applying an inorganic insulating material to steel sheets for use in electrical apparatusincluding the steps of passing the sheets through a bath containing a constituent selected from the group: lime, magnesium oxide; iron oxide; and a constituent selected from the group: silica, water glass; then through a drying oven under conditions corresponding to about two miuntes at about 600 F.

3. The method of applying an inorganic in sulating material to steel sheets for use in electrical apparatus including the steps of passing the sheets through a bath of the liquid insulating material, then through a set of rolls and then through a drying oven to drive off the water content andfinally baking the material by the subsequent annealing of the sheets.

4. The method of applying an inorganic insulating material to steel sheets for use inelectrical apparatus including the steps of passing the sheets through a bath containing lime, iron oxide, and water glass, then through a set of rolls and then, through a drying oven, and finally baking on the material by'the subsequent annealing of the sheets.

5. The method of applying an inorganic insulating material to steel sheets for use in electhe sheets through a bath containing a constitu ent selected from the group: lime, magnesium oxide; iron oxide; and a constituent selected the sheets through a bath of the liquid insulating material, then through a set of rolls and then through a drying oven for about two minutes at about 600 F., and finallybaking on the material by the subsequent annealing of the sheets.'

8. The method of applying an inorganic insulating material to steel sheets for use in electrical .apparatus including the steps of passing the sheets throughabath containing a constituent selected from the group: lime, magnesium oxide; iron oxide; and'a constituent selected from the group: silica, water glass; then through a drying oven under conditions corresponding to about two minutes at about 600 F.,' andfinally baking on the material'by the subsequent annealing of x the sheets.

9. The method of applying an inorganic insulating material to steel sheets for use in elec- 10. The method of applying an inorganic insulating material to steel sheets for use in electrical apparatus including-the steps of passing the sheets through a bath containing a constituent selected from thegroup: lime, magnesium oxide; iron-oxide; and a constituent selected from the group: silica, water glass; then through a drying oven under conditions corresponding to about two minutes at about 600 F., and finally baking on the material by the subsequent annealing of the sheets, the annealing being carried out at about 1450" Fahrenheit.

CHARLES A. SCHARSCHU.' 

